In semiconductor device production processes such as that for producing LSI, the microfabrication technology to which lithography is adopted has heretofore been employed. Since more microscopic processing will positively be in demand, a reduction in wavelength of a light source and enhancement of performance of a resist in lithography are in progress. However, it becomes increasingly difficult to improve resolution with these measures.
Meanwhile, a microfabrication technology utilizing phase-separated structures of a block copolymer has been attracting attention. In the microfabrication technology, regular alignment of the phase separated structures of the block copolymer is required. The following methods have been proposed for attaining the regular alignment of phase-separated structures of block copolymer.
For instance, there has been known a method of forming a microphase-separated pattern of a block copolymer, including: forming a self-assembled monolayer (SAM) on a substrate; coating a photoresist on the substrate to form a line-and-space resist pattern by lithography; performing selective irradiation with an X-ray under an oxygen atmosphere by using the resist pattern as a mask to achieve chemical modification of a part of the SAM; removing the resist pattern; and coating the SAM with the block copolymer, followed by annealing.
Further, there has been known a method of forming a microphase-separated pattern of a block copolymer, including: forming a SAM on a substrate; selectively exposing a part of the SAM by interference exposure to form a chemically modified dot pattern; and coating the SAM with the block copolymer, followed by annealing.
However, since these methods which utilize the SAM are susceptible to a fluctuation in SAM coating rate, and since chemical potential of a molecule forming the SAM is limited, the methods have problems of poor surface free energy controllability of the SAM and unstable alignment of orientation of the microphase-separated pattern of the block copolymer.
Further, there has been known a method of forming a microphase-separated pattern of a block copolymer, including: forming on a substrate a monolayer which is formed of a polymer compound and is called polymer brush by heating for a long time; coating a photoresist on the substrate to form a line-and-space resist pattern by lithography; performing selective irradiation with an X-ray under an oxygen atmosphere by using the resist pattern as a mask to remove a part of the polymer brush; removing the resist pattern; and coating the polymer brush with the block copolymer, followed by annealing.
Further, there has been known a method of forming a microphase-separated pattern of a block copolymer, including: forming a polymer brush on a substrate; coating an electron beam resist on the substrate to form a dot pattern by lithography; performing irradiation with oxygen plasma by using the dot pattern of the electron beam resist as a mask to remove a part of the polymer brush; eliminating the resist pattern; and coating the SAM with a block copolymer, followed by annealing. The method discloses that a dot pitch of the dot pattern of the block copolymer can be narrower than a dot pitch of the dot pattern formed on the electron beam resist.
In these methods using the polymer brush, since the polymer is spread on the surface to form the monolayer, it is possible to stably perform the control of the surface free energy owing to the SAM formed of the silane coupling agent. However, it is necessary to allow a chemical reaction between a hydroxyl group at a polymer end and a Si substrate surface to sufficiently proceed during the formation of the polymer brush and to apply heat energy which sufficiently exceeds activation energy required for the chemical reaction and enables the hydroxy group in the vicinity of Si to sufficiently diffuse at a temperature at which heat decomposition of the polymer does not occur. Therefore, the methods are not practical as the microfabrication technology for semiconductor devices and the like since they require the long-time heat treatment.
Further, there has been reported a phenomenon that an interface part of a polymer remains after the polymer is rinsed with an organic solvent to which the polymer is easily dissolved, when a SAM of a silane coupling agent having a benzophenone structure is formed on a substrate; a polymer is coated on the substrate; and light irradiation is performed to cause a crosslinking reaction between the polymer layer at the interface part which contacts the SAM and the benzophenone. However, the material is not contemplated as the one which is capable of orientation alignment of the microphase-separated pattern of block copolymer and is not proven effective.